Sludge in a Notre Dame Viewfinder

Published: Autumn 2010

As oil-sheened water and tar balls first slopped their way onto the barrier-island beaches of the Gulf Coast in the environmental wake of April’s Deepwater Horizon explosion, the federal government came looking for Joannes Westerink and Andrew Kennedy.

Westerink, a professor of civil engineering and of mathematics, directs the Computational Hydraulics Laboratory, Notre Dame’s node in an increasingly powerful network of computers. The network started as a project he and a colleague from his graduate school days began building to understand the physics of coastal waters.
What eventually became the Advanced Circulation Model (AdCirc) turned out to be a useful tool in predicting the effects that storm surge from powerful hurricanes like Katrina, Rita and Ike could have on the fragile Gulf Coast.
Then came the oil gush. Suddenly the AdCirc Model emerged as the only tool available that could provide the first clues about how the oil would ride on tidal and wind-driven currents as they pulsated up the continental shelf toward land.
“The models that you saw on TV are all deep-ocean models,” Westerink says. Unlike AdCirc, those deep-ocean models, he notes, can’t predict what might happen in water less than 100 meters deep; they can’t account for tides or wind-driven currents or the way water moves into bays and marshes.
Professor Kennedy’s expertise in waves, winds, modeling and measurements as director of ND’s Coastal Hydraulics Laboratory is another key component of the Notre Dame effort to understand the fundamental science of marine oil spills. To that end, the two Notre Dame engineers partnered with colleagues at the universities of North Carolina, Texas and Louisiana State on projects funded by the U.S. Department of Homeland Security and the National Science Foundation.
Satellite images collected at Texas provided much of the data fed into the AdCirc model run on computers at UNC, Texas and Notre Dame. It then took 90 minutes apiece to produce forecasts of oil movement a few days in advance that were constantly being refined by retrospective models based on actual wind measurements. Not fast enough. Westerink says swifter, more precise modeling is especially important to officials in the Federal Emergency Management Agency, who will want ready access to multiple scenarios should they find themselves faced with the nasty prospect of another spill, especially during a hurricane.
Fortunately, as the slick dispersed, the danger of a late-summer hurricane forcing more toxic muck into coastal waterways and communities dissipated. Still, even though it’s a dismal subject, Westerink says he hopes AdCirc’s work on oil transport has just begun. “What we have now is a great historical record of what happened to that oil spill,” he says. Up next are refinements to better account for the many complexities presented by coasts and oceans, weather and climate, and the chemistry of seawater.
“It just shows you how unprepared we are, how poor our understanding of any of this stuff is,” he says. “We have an opportunity to build a little more in-depth knowledge of some aspects of this problem if it keeps on happening, which hopefully it doesn’t.”
_John Nagy is an associate editor of_ Notre Dame Magazine.